An onboard electric system includes: an inverter circuit that outputs an alternating current (AC) to a motor based on an output voltage of a high voltage power supply; a smoothing capacitor that stabilizes a voltage applied between two electric power input electrodes of the inverter circuit from the high voltage power supply; and an electronic control apparatus that controls the inverter circuit based on the output voltage of a low voltage power supply (referring to, for example, Patent document 1).
In this onboard electric system, the electronic control apparatus outputs a discharge control signal to the inverter circuit while a connection between the high voltage power supply and the smoothing capacitor is released by a relay unit. The inverter circuit outputs current to a stator coil of the electric motor based on the output voltage of the smoothing capacitor. In this way, the smoothing capacitor discharges its electric charge through the inverter circuit and the stator coil.
The inventors of the present application have found the following relating to an onboard electric system.
In the onboard electric system of Patent document 1, when an abnormal state happens in a vehicle and the voltage is not outputted to the inverter circuit from the low voltage power supply, the electronic control apparatus cannot output the discharge control signal to the inverter circuit. Therefore, the smoothing capacitor cannot discharge its electric charge through the inverter circuit and the stator coil.